Manufacture of films, foils, and the like containing cellulose derivatives



June 2 3 ,1936. H; R YFQ 2,45,348

MANUFACTURE OF- FILMS, FOILS AND THE LIKE CONTAINING CELLULOSEDERIVATIVES I I Filed Aug. 25, 1955 HENRY DREY'FUS \NVENTDR PatentedJune 23, 1936 I l UNITED STATESPATENT OFFICE MANUFACTUREOF FILMS, Fons,AND THE LIKIVESCONTAINING OELLULOSE DERIVA- 'r a .7 Henry DreyfusLondon, England Application August 25, 1933, Serial No. 686,739

In Great Britain September 9, 1932 9 Claims. o1. 18-15) I This inventionrelates to improvements in celludium may tendto set up liquid currentswhich lose derivative products and particularly to the also disturb therelatively fragile film, it' is admanufacture of films, sheets, foils,for example, vantageous inthe case" when the film'passes those used forwrapping purposes, and like ma through the liquid medium beforecontacting with terials from solutions of cellulose acetate or other thesupporting surface to surround it in this me- '5' cellulose ester orether by wet coagulation procdium'with a protecting shield. Such shieldmay esses. if desired be a continuation of the casing sur- I havediscovered that particularly good results rounding the film in itspassage fromthe' shapare obtained in the manufacture of films, which ingorifice to the surface of the coagulating 10 term is to be understood asincludingfoils, sheets medium and may be formed in one piece with it. 10and the like, from solutions of cellulose acetate When such a shield isemployed means will of V or other cellulose derivative when theextrusion course be adopted to ensure that the medium in orifice orother shaping deviceis situated outside the neighbourhood of the film ismaintained in the coagulating medium, and according to the such acondition that satisfactory coagulation is present invention, therefore,films having a basis obtained, e. g.'by maintaining a slow circulation15 of cellulose derivatives are produced by causing of the medium in thevicinity of the product. a solution of a cellulose derivative to issuefrom In order'to prevent a too rapidi evaporation of a suitable shapingdevice which is outside the any volatile'solvent from the film afterissuing coagulating medium, and then passing the film from'the shapingo'rificeand before its entry into such medium. I into the coagulatingbath, itmaybe desirable to 2' Any suitable means of shaping thefilm-formmaintain a relatively high concentration of soling solution maybe employed. Thus it may be vent in the atmosphere surrounding the film.passed through an elongated slit or between roll- Thus when the shapingorifice is contained in' a ers, and the distance of such shaping devicefrom casing as described in the preceding paragraph,

the coagulating medium may be quite small, for the atmosphere in suchcasing may be maintained Q5 example 1 or 2 inches or'it may be greater,for substantially saturated with solvent vapour, for example, 6 to 8inches or even more; After issuexample, by the presence inside thecasing of a ing from the orifice the film is preferablyreceived vesselcontaining solvent and/ or a fabric or other upon a suitable supportingsurface, for example fibrous material or a porous material as for ex-.

39 a band or drum, and this surface may be wholly ample, pumice,-saturated or substantially satu- 0 or partially immersed inthecoagulating liquid. ratedwith solvent. Suitable means may be pro- Bycausing the film to enter the coagulating mevided for maintaining thefabric or other exdium before contacting'with the supportingsun tendedsurface in a saturated state, as for exface the advantages, described inBritish Patent ample, by immersing a portion of it ina bath con- No.405,692, resulting from contact of the coagutaining solvent or byallowing solvent to drip onto 3 lating medium with both surfaces of theproduct it through suitable orifices. If, however, it is may beobtained. i Y. desired that at least a partial coagulation of the Sincethe films produced according to theprocfilm shall take place before itsentry into the ess of the present invention are in general verycoagulating medium, means may be provided by 40 thin and fragile, andarethus-liable to be diswhich a current of air or other evaporative me:-40 turbed in their passage from the shaping orifice dium is passed incontact withthe film during its to the supporting surface or liquidmedium by passage from the shaping orifice to the coagulatair currents,it is advantageous to surround the ing medium, for example by passingacurrentof shaping orifice with a shield in order to isolate air throughthe casing surrounding the film, or

3 substantially the surrounding atmosphere. Such the film may be sprayedwith a coagulating mea shield may consist merely of metal or other dium.Moreover, the use of both these means sheets surrounding the shapingorifice and exin conjunction is of course not excluded.v tendingdownwards towards the supporting sur- If desired, a stretch may beimparted to the face or the surface of the liquid, but preferably filmsduring their production. Thus the film may a casing isemployed in whichthe shaping orifice be taken up on a drum or other support travel- 50 issituated, the bottom of this casing either dipling at a speed greaterthan that at-whi'ch'the ping into the coagulating medium or making closefilm issues from the shaping device, or, alternacontact with the surfaceof the supporting band, tively, the films may be stretched laterallyand/or drum or the like. Further, since the rotation of transversely bymeans of the apparatus described t supp t g surface in thecoagulating-mein U S. Patent No. 2,034,716.. r 55 Any suitable solventmay be employed for forming the solution of the cellulose acetate orother cellulose derivative, as, for example, relatively low boilingsolvents or solvent mixtures such as acetone, acetone and alcohol,methylene-ethylene-ether and mixtures of methylene or ethylene chloridewith ethyl or methyl alcohol, or of methyl or ethyl acetate with .methylor ethyl alcohol. Higher*boiling'solventsmayalso be used, for example,methyl ethyl ketone, dioxane, diglycerol tri-ether, diacetone alcohol,esters or ether-esters of olefine and .poly-olefinelglycols, forexample, glycol mono-acetate I01 :methyl glycol mono-acetate, ethyllactate, and homolo-gues and substitution products of methylene ethyleneoxide and dioxane, as for example the esters and ether-esters ofdioxane-dicarbinol. .Mixturesof solvents, e. g. a mixture of a low andhigher boil-- ing solvent, may also be employed. The filmformingsolutionsmay also contain diluents, for example water, glycol, glycerol.or other hydroxy compound, benzene, toluene, kerosene,rhexahy-.dro-benzene or other aromatic-aliphatic or alicyclic hydrocarbon, andhalogenated hydrocarbons, for example, tetrachlorethane anddichlorethylene. High boiling solvents or plasticizers .for thecellulose derivative .may also be incorporated in the film-formingsolutions, and examples of such substances are the aoetins, alkylphthalates, for example :diethyl :phthalates, and arylsulphonamides, :asfor example the monomethylated or .ethylated xylene :sulphonamides.

and 1380;819. .Coagulating baths containing the same solventzas thatpresent in the film-forming solution, as is described in British PatentNo. 405,=6.'Z6,maybeadvantageously employed. Again, the coagulating bathmay be one in which the solvent :of the film-forming solution isimmiscible or is miscible only in certain proportions as described inBritish Patent No. 407,673. Thus, for example, :an :acetone solution ofcellulose acetate maybe coagulated in a bath consisting of orcontainingbenzine, kerosene or other para'flin hydrocarbon. Again, coagulatingmedia containing glycerine, sugars or other polyhydroxycompoun'ds may beemployed, see for example British Patent No. 406,986. The =use ofsolutions 'of inorganic salts, for example, sodium chloride or calciumchloride, :as is described in British Patent No. 406,337, has, however,been found to be of particular value in connection with the presentprocess.

The period of contact of the film with the coagula-ting media may besuch that when they issue therefrom they contain substantially noresidual solvent, in which case they may be directly dried, with orwithout previous washing or other treatment to remove any adherentcoagulating media. If, however, on issuing from the coagulating bath,the films contain residual solvent,theymay be washed, for example with asalt solution or with dilute solutions of solvents in order to removesuch solvent and may then be dried. Preferably however, residualsolvent, or at least a small percentage of solvent, for example the last5 to 10% based on the weight of the material, is removed by evaporation,for example by passing the films through drying chamhers or over heatedsurfaces.

The drying of the films may take place on the drum or other support onwhich they are produced or in a separate drying apparatus. In the formercase the upper part of the ascending side of the drum may be providedwith an enclosing heating segment, which may be heated by steam pipes orin any other suitable manner so that the V films are practicallycompletely dried, and they may then be passed to suitable take-uprollers. When-drying takes place in a separate apparatus, the .afi-lms:may pass from the drum or other support to the drying apparatus, forexample a steam heated drum.

Examples of apparatus which may be employed according to the presentinvention are illustrated in {the accompanying drawing, wherein Figure 1shows a cross-sectional elevation of one form of apparatus comprising adrum which is partially immersed in the coagulating medium,

Figure 2 is a cross-sectional elevation of another form of apparatuswherein the drum is completely immersed in the coagulating medium, and

Figure 3 .isza cross-sectional elevation of a portion of a similarapparatus.

Figured illustrates an apparatus comprising a vessel 5 for coagulatingmedium, a. drum 6 which rotates in such medium, and a valve-controlled Iinlet FI and. -.an outlet .8 for coagulating medium. Thefihnd isextruded through a suitable shaping device I10 connected by means of apipe I I with a :supply of film-forming solution, and contacts with thedrum 5 from which it passes'to a roller and .thence to suitable washingand drying devices. The shaping device I0 is situated in a casing I'2,.oneside of the casing being formed by an extension :of an end of thevessel 5, while the opposite side of the casing extends downward towardsthe coagulating drum without actually touching the surface of this drum.A hinged flap -I3 is fitted in the side of the casing to allow of accessto the shaping device.

Figure 2 illustrates a similar form of apparatus comprising ra drum 6rotating in a vessel 5 provided with a valve-controlled inlet I and anoutlet 8 for coagulating medium. Both inlet and outlet are formed by aslotted or perforated pipe extending across the Width of the vessel, soas to obtain auniform introduction and withdrawal of coagulating'mediumacross the Width of the vessel. The film '9 extruded from the shapingdevice "I11, which is situated Within a casing I2 and which isconnectedwith the supply of film-forming solution by a pipe II, contacts with thedrum 6 and passes from the drum over a roller to washing and dryingdevices. The drum 6 is entirely immersed in the coagulating medium, andone side of the casing I2 surrounding the film-forming-device isextended downwardly below the surface of the coagulating medium until italmost contacts with the drum. In order to assist circulation of thecoagulating medium the portion of this 'side of the casing below thesurface of the coagulating medium may be perforated, or maybe formed ofmetal gauze. Towards the bottom of one side of the casing, but above thelevel of the coagulating medium, is a shallow vessel I 5 which may befilled with solvent liquid in order to maintain the atmosphere in thecasing substantially saturated with solvent, and in order to assist inachieving this object a piece of suitable absorbent fabric or othermaterial I6 is suspended from the top of the casing so that its loweredgev dips in the solvent contained in the vessel l5; Doors I3 and I4are fittedto the easing to allow of access to the film-forming deviceand the vessel l5 andfabric I6. Figure 3-illustrates a detail ofasimilar-apparatus in which means are provided for effecting evaporationof some of the solvent from the film before its entrance into .thecoagulating medium. As inv the other illustrations the apparatuscomprises a supply pipe H and a shaping device H), which is situatedwithin a casing I2 and from which the film 9 is extruded, the filmcontacting with a supporting drum 6. Coagulating medium is withdrawnfrom the;v'essel 5 by an outlet pipe 8, similar to that described inconnection with Fig. 2, An inlet for evaporative medium is provided atI! and an outlet for such medium at .IB, both inlet'and outlet beingfitted with valves Example A 25% solution of cellulose acetate inacetone is extruded through a shaping orifice contained in a suitablecasing, as illustrated, for example, in Figure 2, and after passing forabout three inches through the atmosphere contained in the casing itenters a coagulating bath consisting of a 25% aqueous solution ofcalcium chloride. After passing for about two to four inches through thecoagulating bath the film passes round a rotating drum Where thecoagulation of the film is completed. The film is then washed, firstwith dilute aqueous calcium chloride solution, for example 5-8%, andthen with water, is dried on a steam heated drum, and wound.

While the invention is of particular value in relation to the productionof films from solutions of acetone-soluble cellulose acetate, yet it isalso of value for the manufacture of such products containing othercellulose acetates or other derivatives of cellulose, for examplecelulose formate, propionate, butyrate, nitroacetate or other organicester or mixed ester of cellulose, cellulose nitrate, methyl, ethyl,butyl or benzyl cellulose or other cellulose ether or mixed ether, andmixed ether-esters, for example ethyl cellulose acetate andoxy-ethyl-cellulose acetate.

While particular methods of carrying out the present invention have beendescribed above, it is to be understood that the invention broadlycovers the production of films, foils, sheets and the like fromsolutions of cellulose derivatives, by passing the solutions intocoagulating baths from shaping devices which are not in contact withsuch baths, and also includes the apparatus described in connection withthe preferred forms of the invention.

The term encompassing gaseous medium as employed hereinafter in theclaims is to be construed to means a gaseous medium which contacts withboth sides of the shaped product.

What I claim and desire to secure by Letters Patent is:-

1. Apparatus for the manufacture of films, comprising a vessel forcoagulating liquid, means for circulating coagulating liquid throughsuch vessel and for maintaining a constant level of coagulating liquidtherein, a device having a slot formed therein for shaping thefilm-forming solution disposed above the level of liquid in said vesseland adapted to extrude the'shaped material'first through an encompassinggaseous medium and then into the said liquid, a casing surrounding theshaping device and extending from such'device to the surface of thecoagulating liquid adapted substantially toisolate the said encompassinggaseous medium from the surround .ing atmosphere, and means forintroducing the vapor of a liquid into the interior of such casing.

2. Apparatus for the manufacture of. films,

comprising" a vessel for coagulating liquid, means for circulatingcoagulating liquid through such vessel and for maintaining a constantlevel of coagulating liquid therein, a device having a slot formedtherein forshaping the film-forming solution disposed above the level.of liquidin said vessel and adapted to extrude the shaped material firstthrough an encompassing gaseous medium and then intothe said liquid, acasing surrounding the shaping device andextendingfrom such device tothe'surface of the coagulating liquid adapted substantially. to isolatethe said encompassing gaseous medium from the surrounding atmosphere,means for introducing the vapor of a liquid into the interior of suchcas- 2 ing, and a rotatable drum positioned at least partially below theliquid level in the vessel for coagulating liquid and adapted to receiveand support the shaped material.

3. Apparatus for the manufacture of films,

comprising a vessel for coagulating liquid, means for circulatingcoagulating liquid through such vessel and for maintaining a constantlevel of coagulating liquid therein, a device having a slot formedtherein for shaping the film-forming solution disposed above the levelof liquid in said vessel and adapted to extrude the shaped mate rialfirst through an encompassing gaseous medium and then into the saidliquid, a casing surrounding the shaping device and extending from suchdevice to the surface of the coagulating liquid adapted substantially toisolate the said encompassing gaseous medium from the surroundingatmosphere, means for introducing the vapor of a liquid into theinterior of such casing, a rotatable drum positioned at least partiallybelow the liquid level in the vessel for coagulating liquid adapted toreceive and support the shaped material after such material has passedthrough a portion of the coagulating liquid, and a shield adaptedsubstantially to isolate the portion of the coagulating liquidsurrounding the shaped material along its path from the surface of thecoagulating liquid tothe surface of the drum from the remainder of thecoagulating liquid.

4. Process for the manufacture of films, which comprises forming asolution of an organic derivative of cellulose into the required shape,passing the shaped product through an encompassing gaseous medium whileretarding evaporation of solvent from the shaped product by introducingsolvent vapor into said gaseous medium from an external source, andthereafter coagulating the shaped product by passing it into acoagulating bath.

5. Process for the manufacture of films, which comprises forming asolution of cellulose acetate into the required shape, passing theshaped product through an encompassing gaseous medium while retardingevaporation of solvent from the shaped product by introducing vapor ofsaid solvent into said gaseous medium from an external source, andthereafter coagulating the bath.

6. Process for the manufacture of films, which comprises forming asolution of cellulose acetate into the required shape, passing theshaped product for a distance of 1 to 8 inches through a confinedencompassing gaseous medium while retarding evaporation of solvent .fromthe shaped product by introducing vapor or said solvent into saidgaseous medium from an external source, and therafter coagulating theshaped material by passing it into a coagulating bath.

'7. Process for the manufacture of films, which comprises forming asolution of cellulose acetate into the required shape, passing theshaped product for a distance of 1 to 8 inches through a confinedencompassing gaseous medium while retarding evaporation of solvent fromthe shaped product by introducing vapor of said solvent into saidgaseous medium from an external source, thereafter coagulating theshaped material by passing it into a coagulating bath, and receiving iton a moving supporting surface which is at least partially immersed insaid bath.

8. Process for the manufacture of films, which comprises forming asolution of cellulose acetate into the required shape, passing theshaped product for a distance of 1 to .8 inches througha confinedencompassing gaseous medium while retarding evaporation of solvent fromthe shaped product by introducing vapor of said solventinto said aseousmedium from an external source, and thereafter coagulating the shapedproduct by passing it into a coagulating bath so that coagulating liquidcontacts with both sides of the shaped product and then contacting theshaped product with a moving supporting surface which is at leastpartially immersed in said bath.

9. Process according to claim 8 wherein the portion of coagulatingmedium through which the shaped product passes before contacting withthe supporting surface is substantially separated from the remainder ofthe liquid.

HENRY DREYFUS.

